Summary

Publications: The results of the study have been presented as 19 scientific publications (7 articles, 5
conference proceedings, and 7 abstracts), three of which without coauthors.

Structure of the work: The thesis consists of the Introduction, five Chapters, Conclusions,
Recommendations, the Bibliography of .280.references, and Summary in three languages. The work
contains 172 pages of the text body, 49 Figures, and 8 Tables.

The purpose of the thesis. The study of the nonequilibrium charge carriers (NCC) relaxation in bulk
GaSe at low and middle levels of excitation, as well as at high excitation in GaSe EHP, in
GaAs/Al0,3Ga0,7As quantum wells. and in CdSe/ZnS quantum dots .

Novelty and scientific originality. For the first time, in the PL of GaSe the contribution of the
“phononless” radiative Auger-recombination of two indirect excitons is established. The novel technique
of the time-resolved spectra is applied to study the EHP PL. The new theory of the PL spectra kinetics is
submitted for consideration: after short time, the spontaneous emission from direct and indirect bands,
which is attributed to NCC thermalization, is replaced by the PL from the indirect band, which is
determined by the electron-electron scattering and then by the PL from the indirect band, which is
related to the exciton-exciton scattering. The PL decay characteristic time is measured. In addition, for
the first time, constants of the processes of the electron-electron and exciton-exciton scatterings were
evaluated. In GaSe, the NCC density of a Mott transition was calculated in a new way – from the
equality of values of the exciton Rydberg and the BGR. By the direct measuring of the EHP stimulated
emission decay characteristic time, the transient quantum well BGR decay characteristic time is
determined. At high concentrations of the excited electron–hole pairs, the retardation of charge carrier
relaxation over the quantum size energy levels in CdSe/ZnS quantum dots was recorded experimentally.

The scientific issues considered in the thesis: in bulk GaSe, at different levels of excitation, new
relaxation channels of NCC were revealed; the GaAs quantum well transient BGR decay characteristic
time was determined; the fast zero-phonon energy relaxation of hot electrons in CdSe/ZnS quantum dots
was observed and the retardation of the charge carrier relaxation over the quantum size energy levels in
quantum dots at high concentrations of excited electron–hole pairs was detected.

The research objects are the NCC relaxation processes in GaSe crystal, in GaAs/Al0,3Ga0,7As quantum
wells, and in CdSe/ZnS quantum dots.

Scientific significance of the thesis consist in the discovery of a number of fundamentally new results,
which are important for understanding of both the NCC relaxation processes in bulk and quantumdimensional
structures, and of the influence of the large density NCC relaxation processes on the
respective structures optical properties.

The implementation and practical significance. The obtained results may be used to create optical
switching elements on the base of plasma reflection, which could shape ultrashort pulses of specified
parameters in the terahertz frequency range. In addition, a next promissing possible application is the
creation of saturable absorbers and optical modulators for both active and passive modelocking in the
compact ultrafast solid-state lasers.